1. Field
The present specification relates to methods for firing ware in a furnace and, more particularly, to methods for controlling a furnace atmosphere during firing of ware.
2. Technical Background
Ceramic ware is often heated or “fired” in a kiln or furnace. If the ware is not properly fired, it can crack or otherwise fail to form correctly. One problem associated with improper firing is uneven heating, such as when there are temperature differences between each piece of ware. This can occur from introducing heated gas into a heating space of a furnace or kiln in which some pieces of ware are positioned close to the entrance of the heated gas and other pieces of ware are positioned in the inner portions of the heating space further away from where the heated gas enters. The kiln can have regions in the heating space at higher temperatures resulting in overheating of the ware, and regions at lower temperatures resulting in underheating of the ware. Excessive overheating can cause ware to crack. Excessive underheating can adversely affect the final desired properties of the formed ware. Thus, it may be desirable to have a more uniform and controlled temperature distribution throughout the heating space of a kiln during firing.
Another problem associated with improper firing is temperature differentials within each piece of ware. Ware containing organic compounds that are removed (via burning) by oxidation and/or combustion during the firing cycle tend to produce large amounts of exothermic heat. The exothermic heat can produce a temperature differential within each piece of ware. In addition, oxygen present in the atmosphere tends to react with the organic compounds thereby accelerating release and increasing the exothermic reaction. Large temperature differentials within ware can cause cracking. Thus, it may be desirable to minimize the temperature differential and cracking within each ware.
Accordingly, alternative methods for providing atmosphere control during firing cycles to produce crack-free ware are needed.